Relationship between I2 Imidazoline Binding Sites and Monoamine Oxidase B in Livera
Article first published online: 6 FEB 2006
Annals of the New York Academy of Sciences
How to Cite
REMAURY, A., ORDENER, C., SHIH, J. and PARINI, A. (1999), Relationship between I2 Imidazoline Binding Sites and Monoamine Oxidase B in Liver. Annals of the New York Academy of Sciences, 881: 32–34. doi: 10.1111/j.1749-6632.1999.tb09338.x
- Issue published online: 6 FEB 2006
- Article first published online: 6 FEB 2006
ABSTRACT: Biochemical and pharmacologic studies suggest that I2 imidazoline binding sites (I2BS) represent a heterogeneous family of membrane proteins. Indeed, the imidazoline binding sites located on monoamine oxidases (MAO) A and B display different pharmacologic properties. Recent results suggest that in liver and brain, I2BS may be located on proteins distinct from MAOs. The following observations indicate that in liver and brain, [3H]idazoxan binds exclusively to I2BS located on MAO-B: (1) size exclusion chromatography of digitonin-solubilized preparations from rabbit and human liver showed that [3H]idazoxan-specific binding eluted only in two peaks (∼175,000 and ∼100,000 Da, corresponding to 90% and 10% of the recovered [3H]idazoxan binding) which also contained MAOs as determined by [14C]tyramine oxidation and Western blot analysis; (2) according to previous results obtained in various human and rat tissues, experiments performed in mice liver and brain showed that idazoxan was a potent inhibitor of [125I]-AZIPI photoincorporation to MAO-B but not to MAO-A; (3) in MAO-deficient transgenic mice, [3H]idazoxan binding to liver and brain membranes was completely abolished in MAO-B knockout mice and was not affected in MAO-A knockout mice. Together, these results show that in both liver and brain, I2BS are located exclusively on MAO-B. The imidazoline binding site on MAO-A, which photoincorporates [125I]-AZIPI and displays a low affinity for idazoxan, may not belong to the family of the I2 imidazoline binding sites.